You can learn fundamentals in SFIV that you can apply to SFV, however, you have to limit your play style in my experience. Limit use of focus attacks, little to no backdashing to break yourself out of the habit of relying on invincible back dashes, no jumping like a fucking mad man when you get a knockdown, no crouch teching, etc. At least, that's what I had to do before I felt I was making progress in prepping for SFV by playing SFIV.
It'll make your play in SFIV seem hella scrubby.
It'll make your play in SFIV seem hella scrubby.